Carbon Dioxide (CO2) has been the greenie's favorite greenhouse gas. Greenhouse gases in the atmosphere are blamed for global warming. These are gases that are transparent to visible light and near visible light (short infrared and some ultraviolet) and opaque to long wave infrared. Solar heat comes to the earth and warms it as visible light. The warmed earthly objects, rocks, soil, vegetation, everything, throws off heat by radiating long wave infrared. On the night side of earth, the long wave infrared goes up into space carrying heat with it. Overall earthly temperature is believed to be the result of a balance between incoming Solar heat on the day side, and outgoing infrared radiation on the night side. Increased levels of greenhouse gas block the long wave infrared and are believed to increase the average temperature of the earth.
Now the Economist has a long piece about the evils of methane in the atmosphere. It's dreadful. Methane is the bulk of natural gas, and flatulence. It comes from leaks in natural gas pipelines and gas wells, as well as flatulence among cows, of which there are lot on the earth.
Only one little problem with the methane scare story. The Economist shows a graph starting in 1984 and going to 2018. Methane in the atmosphere has increased from 1650 parts per BILLION, to 1850 parts per BILLION.
Rescale from parts per billion to the more widely used parts per million, and the methane levels become 1.65 PPM and 1.85 PPM.
We have good laboratory data going back about 100 years on carbon dioxide levels. They used to be 350 some PPM, and now are getting close to 400 PPM.
Somehow I don't think less than 2 PPM of methane will ever make much difference against 400 PPM of carbon dioxide.
And for that matter, plain old water vapor is as strong a greenhouse gas as carbon dioxide or methane, and the atmosphere contains about 10000 PPM of water vapor. It varies from time to time, the weathermen call it humidity and report it on the nightly news. As I write this, it's raining outside, which means 100% relative humidity. Since there is about 25 times more water vapor in the atmosphere than carbon dioxide, I don't worry much about carbon dioxide. Compared to the water vapor, there just isn't enough carbon dioxide to worry about. And the water vapor is better than 1000 times more plentiful than methane.
On a planet that is three quarters ocean, nothing is going to reduce the water vapor content of the atmosphere. Plus the water vapor comes down as rain, which most places need more of.
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